1. Field of the Invention
The present invention relates to a recording medium suitable for ink-jet recording, and a method of ink-jet recording employing the recording medium.
2. Related Background Art
Non-treated ordinary paper and coated paper having an ink-receiving layer have been conventionally used as recording mediums for ink-jet recording.
The non-treated ordinary paper, when used for recording with aqueous ink, involves disadvantage that formed images undergo running or feathering, giving neither high density of images nor high resolution of the images.
To offset the disadvantage, various ink-jet recording mediums have been proposed which comprise supporting paper and an ink-receiving layer formed thereon for absorbing aqueous ink. For example, Japanese Patent Application Laid-Open No. 56-148585 describes coated paper comprising ink-absorbing base paper and an ink-receiving layer formed thereon with inorganic porous pigment: Japanese Patent Application Laid-Open No. 61-135785 describes an ink-jet recording medium containing a hydrotalcite compound; and Japanese Patent Application Laid-Open No. 61-57380 describes an ink-jet recording medium comprising an ink-receiving layer containing porous inorganic pigment and a slightly soluble magnesium compound.
The recording mediums of the prior art as described above have advantages that neither feathering of ink nor fattening of printed letters occurs and high resolution of images can be achieved. These recording mediums, however, do not readily give high image density. In the case where silica or alumina having a large specific surface area is employed as described, for example, in Japanese Patent Application Laid-Open No. 59-185690 for the purpose of achieving higher image density, another disadvantage is involved that the recording dye discolors with lapse of time and the recorded image deteriorates under normal environmental conditions, for example, only by posting on an indoor wall.
The above described indoor discoloration can be retarded by forming the ink-receiving layer by use of calcium carbonate or kaolin having a small specific surface area, or a hydrotalcite compound as disclosed in Japanese Patent Application Laid-Open No. 61-135785, and the like. However, the density of the resulting image is low, and feathering or fattening of letters occurs, thus no clear image being given.
Moreover, when the aforementioned pigment or pigments having an average particle diameter of 7 .mu.m or larger are used solely or combinedly, white haze of the printed letters is liable to be caused. This white haze is a phenomenon characteristic to lightly coated paper having a thin ink-receiving layer, and is considered to be caused by the fact that the thin coating layer does not completely cover the fiber exposed on the surface of the base paper, and the dye absorption ability of the exposed fiber portion is low, thus the image density at the exposed fiber portion being decreased. Such problems can naturally be solved if the ink-receiving layer is formed thick to cover the entire fiber of paper. However, such recording mediums having thick ink-receiving layer are not paper-like and are undesirable also in view of cost and weight.
The fattening of the printed letters can be avoided by adding a cationic polymer having high dye-absorbing power into the ink-receiving layer, but preservability of the recorded images is deteriorated thereby.
As described above, the conventional coated paper having a thin ink-receiving layer cannot achieve high density of images without feathering of images nor fattening of letters, and cannot avoid white haze and indoor discoloration, not easily satisfying the general requirements for ink jet-recording mediums at the same time.